Field of the Invention
The present invention relates to an emergency steering system for a vehicle, and more particularly, to an emergency steering system for a vehicle, which enables steering to be easily carried out by changing a gear ratio using a planetary gear in the event of failure of a main steering device for a vehicle.
Description of Related Art
Referring to FIG. 1, a vehicle steering apparatus (especially, a commercial vehicle steering apparatus) includes a gear box 10 which is connected to a steering wheel 28 in a driver's seat, and a pitman arm 30 which is connected to the output shaft of the gear box 10 and is a type of output link. The pitman arm 30 is connected to a driving wheel hub through a drag link, a knuckle arm, etc.
When a decelerating force is output from the gear box 10 to the pitman arm 30 depending on the steering of the steering wheel 28, the pitman arm 30 rotates (angular rotation) clockwise or counterclockwise, in which case the driving wheel hub is steered right and left through the drag link and the knuckle arm by torque (rotational force), steering driving wheels.
When such a steering apparatus has failure, there is a need for an emergency steering device to urgently steer and move a vehicle to a safe place within a certain distance.
FIG. 2 illustrates a conventional emergency steering system, and reference numeral 10 denotes a gear box connected to a steering wheel.
The gear box 10 has a predetermined gear ratio for power steering, and power steering oil for power steering operation is circulated in the gear box 10.
A main steering device has a structure in which a main pump 14 is connected to an engine 12 to circulate the power steering oil.
Accordingly, the steering oil stored in a main oil tank 16 is supplied to the gear box 10 via a control valve 18 by the operation of the main pump 14 together with the engine 12, with the consequence that the gear box 10 is smoothly lubricated for the power steering operation thereof.
In the instant case, the power steering oil supplied to the gear box 10 is returned back to the main oil tank 16 through a check valve 20.
Meanwhile, when a steering force is lost due to the malfunction of the main pump, an emergency steering device is operated such that the steering wheel is operable, thereby enabling the vehicle to be moved in a desired direction.
The emergency steering device includes an electric motor 22, a sub-pump 24 connected to the electric motor 22, a sub-oil tank 26, etc.
When a steering force is lost due to the malfunction of the main pump, the sub-pump 24 is operated by the driving of the electric motor 22 so that the steering oil stored in the sub-oil tank 26 is supplied to the gear box 10 via the control valve 18. Consequently, the gear box 10 is smoothly lubricated for the power steering operation thereof, and the vehicle may be moved in a desired direction.
For reference, a controller determines that the emergency steering device is operated in an emergency state in which a steering force is lost when the vehicle speed is equal to or less than 1 km/h and the pumping flow rate by the main pump is equal to or less than 5 L/min.
However, although the conventional emergency steering system has an advantage of smoothly inducing a steering force using the electric motor and the sub-pump even when the engine is not driven, it may lead to an increase in manufacturing cost of vehicles since the motor pump unit including the electric motor and the sub-pump is very expensive. Particularly, the emergency steering system may not be operated because power is not supplied to the electric motor in the event of failure of batteries.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the related art already known to a person skilled in the art.